A structure of a liquid-cooled motor is described with reference to FIG. 1 (a front view) and FIG. 2 (a side sectional view taken along A-A′ section of the front view). The motor rotates with its rotor 107 about its rotation axis 105. Alternating current flows in the rotor 107 and heat is generated due to an eddy current loss based on the alternating current. When the heat generation grows to increase the motor temperature, problems will arise, such as a decrease of generated torque of the motor and an increase of inverter failure rate. As such, cooling liquid is introduced into the motor through cooling liquid ports 101 and circulated through a cooling liquid flow path 103 formed around the motor.
Incidentally, an example of application of such a motor is for electric vehicles. An electric vehicle has an economical advantage that electricity therefor costs less in comparison to gasoline for a current gasoline vehicle. In addition, the electric vehicle has environmental advantages that it emits no exhaust gases such as NOx and COx, discharging no causative agents for atmospheric pollution and global warming and is quieter in engine sound than the gasoline vehicle, causing less noise problems.
On the other hand, the electric vehicle has a disadvantage that it cannot get sufficient mobile performance in comparison to the gasoline vehicle. For the electric vehicle, the criterion of practical use is whether it can obtain a mobile performance equivalent to or more than that of the gasoline vehicle by the combination of motor and battery.
In order to solve such problems associated with the electric vehicle, it is considered an important proposition to lengthen travel distances by increasing battery performance and reducing recharging times. Simultaneously, as an elemental technique for realizing that, motors must be reduced in size and weight, improved in performance and durability and reduced in cost.
With this respect, in order to improve motor efficiency and performance, refinement for increasing magnetic flux density of magnets to be used for the motor, refinement for increasing winding density of lead wires, development for methods of controlling inverters and the like are currently under way. Such modifications of designs are necessary, but a huge amount of cost and time for development will be necessary.
When a currently available motor is used for an electric vehicle, problems are that its output is small in relation to battery capacity and motor output is small. For output, when the motor has too high a temperature, its output will further decrease.
A decrease in output will more quantitatively be described. An electric vehicle uses mainly a polyphase induction motor or a permanent magnet-based synchronous motor. When copper lead is used for armature windings, resistance of the copper lead will increase as much as 12% with an increase in temperature of 30° C. Along with this, an induced voltage that is in proportion to a generated torque of the motor will also decrease. When permanent magnets are used for the motor, magnetic flux density will decrease, depending on their material, due to an increase in temperature. For reference, when barium ferrite is used as a permanent magnet material, the magnetic flux density will decrease as much as 5.4% with an increase in temperature of 30° C. Accordingly, the torque will decrease for the same percentage. Due to these factors, some motors may decrease their torques nearly 20% with an increase in temperature of 30° C.
It is also said that a failure rate for an inverter will usually double as the surrounding temperature increases for 10° C. (10° C. law). For this respect, the increase in temperature of the motor must be suppressed to the minimum.
Suppression of increase in temperature of a motor is extremely important for maintaining motor efficiency and minimizing failures. To this end, performance of a motor-cooling system must securely be guaranteed. Otherwise, the temperature of a motor or an inverter for drive control would excessively increase, preventing a wanted output from being obtained at high-revolution, high-output ranges.
To cope with an increase in temperature of a motor, measures are taken currently, such as a combined use with air-cooling, an increase of cooling capacity by enlarging a heat sink for preventing inverter overheating or an increase of cooling capacity per unit time by enlarging a pump for cooling liquid circulation. These solutions will, however, be contradictory to the objectives as described above, such as reduction in size and weight, improvement in performance and durability and reduction in cost for a motor.
On the other hand, water in which water molecules are finely dispersed by a magnetic force for activation (active water) is known. Such active water and treatment processes therefor are disclosed in detail in the following literatures.
Patent literature 1: Japanese Unexamined Patent Publication No. 1993-293491 (in its entirety)
Patent literature 2: Japanese Unexamined Patent Publication No. 1996-155442 (in its entirety)
The active water is highly surface-active, dissolving and permeating and is therefore known for possessing effects such as removing stains very well and inhibiting scale and slime buildup in pipes. Also the active water is in a highly energized state in which electron-exciting action is exerted to actively move electrons and is therefore known for having effects such as being stable because substances contained in a liquid are uniformly present as ions, inhibiting proliferation of aquatic algae and preventing harmful compounds from being produced by ionic bond.